(define (is-primes x)
  (define (smallest-divisor n)
    (find-divisor n 2))
  (define (find-divisor n test-divisor)
    (cond ((> (square test-divisor) n) n)
          ((divides? test-divisor n) test-divisor)
          (else (find-divisor n (+ test-divisor 1)))))
  (define (divides? a b)
    (= (remainder b a) 0))
  (define (prime? n)
    (cond ((= n (smallest-divisor n)) #t)
          (else #f)))
  (define (next-odd n)
    (cond ((even? n) (+ n 1))
          (else (+ n 2))))
  (prime? x))
